Method for increasing a surface area of epitaxial structures in a mixed N/P type fin semiconductor structure by forming multiple epitaxial heads

ABSTRACT

A non-planar semiconductor structure includes mixed n-and-p type raised semiconductor structures, e.g., fins, having epitaxial structures grown on top surfaces thereof, for example, epitaxial silicon and silicon germanium, naturally growing into a diamond shape. The surface area of the epitaxial structures is increased by removing portion(s) thereof, masking each type as the other type is grown and then subsequently modified by the removal. The removal may create multi-head (e.g., dual-head) epitaxial structures, together with the neck of the respective raised structure resembling a Y-shape.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention generally relates to non-planar semiconductorstructures with epitaxial structures on top surfaces of raisedsemiconductor structures. More specifically, the present inventionrelates to such structures with mixed n-and-p-type raised structures,and increasing the surface area of the epitaxial structures withoutadding additional epitaxial material.

2. Background Information

With the ever-shrinking sizes of semiconductor devices, creativity indesign has allowed the decrease in size to continue. For example,non-planar devices with raised semiconductor structures (e.g., “fins”)were an important breakthrough, while the inclusion of epitaxialsemiconductor structures at the top surface of the raised structuresfurther extended the breakthrough of non-planar devices. Complicatingthe situation is the inclusion of mixed n-and-p-type raised structureson the same substrate, requiring different epitaxial materials. Asdimensions continue their downward march, the real-world sub-structuresproduced stray farther and farther from the ideal dimensions and/orshape. For example, the raised structures have a tapered shape, gettinggradually larger from tip to base, the tip being the location for theepitaxial structure. In turn, the epitaxial structure is smaller, thesurface area of which largely determines current throughput, and, hence,a key performance contributor.

Therefore, a need continues to exist for a way to improve semiconductorperformance, and, in particular, current throughput, bearing in mindexisting design constraints with regard to the total height of theraised structure with epitaxial structure on top.

SUMMARY OF THE INVENTION

The shortcomings of the prior art are overcome and additional advantagesare provided through the provision, in one aspect, of a method offabricating a non-planar semiconductor structure. The method includesproviding a semiconductor structure, the structure including asemiconductor substrate, at least one first raised semiconductorstructure of a first type coupled to the substrate, and at least onesecond raised semiconductor structure of a second type coupled to thesubstrate. The method further includes growing at least one firstepitaxial structure on a first top surface of one or more of the atleast one first raised structure, the at least one first epitaxialstructure including at least one first epitaxial material, and growingat least one second epitaxial structure on a second top surface of oneor more of the at least one second raised structure, the at least onesecond epitaxial structure including at least one second epitaxialmaterial. The method further includes increasing a first surface area ofthe at least one first epitaxial structure by removing a top portionthereof, the top portion having bottom sides longer than top sidesthereof, and increasing a second surface area of the at least one secondepitaxial structure by removing a top portion thereof, the top portionhaving bottom sides longer than top sides thereof.

In accordance with another aspect, a semiconductor structure isprovided. The structure includes a semiconductor substrate, at least onefirst raised semiconductor structure coupled to the substrate, the firstraised structure being one of N type and P type, and at least one secondraised semiconductor structure coupled to the substrate, the secondraised structure being the other of N type and P type. The structurefurther includes at least one first epitaxial structure of a firstepitaxial material coupled to the at least one first raisedsemiconductor structure, the at least one first epitaxial structureincluding at least two first epitaxial head structures, and at least onesecond epitaxial structure of a second epitaxial material coupled to theat least one second raised semiconductor structure, the at least onesecond epitaxial structure including at least two second epitaxial headstructures.

These, and other objects, features and advantages of this invention willbecome apparent from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts one example of a starting structure for a non-planarsemiconductor structure, including a raised structure of a first type(e.g., P type) and a raised structure of a second type (e.g., N type),in accordance with one or more aspects of the present invention.

FIG. 2 depicts one example of the structure of FIG. 1 after masking thefirst raised structure in accordance with one or more aspects of thepresent invention.

FIG. 3 depicts one example of the structure of FIG. 2 after recessingthe second raised structure below a top surface of filler materialsurrounding the raised structures in accordance with one or more aspectsof the present invention.

FIG. 4 depicts one example of the structure of FIG. 3 after creating anepitaxial structure of a first type on the recessed top surface of thesecond raised structure in accordance with one or more aspects of thepresent invention.

FIG. 5 depicts one example of the structure of FIG. 4 after removal ofthe mask above the first raised structure in accordance with one or moreaspects of the present invention.

FIG. 6 depicts one example of the structure of FIG. 5 after creating aconformal layer of protective material (i.e., a mask) over the epitaxialstructure on the second raised structure and over a top surface of thesurrounding filler material in accordance with one or more aspects ofthe present invention.

FIG. 7 depicts one example of the structure of FIG. 6 after recessingthe first raised structure below a top surface of filler materialsurrounding the raised structures in accordance with one or more aspectsof the present invention.

FIG. 8 depicts one example of the structure of FIG. 7 after creating anepitaxial structure of a second type on the recessed top surface of thefirst raised structure in accordance with one or more aspects of thepresent invention.

FIG. 9 depicts one example of the structure of FIG. 8 after removal ofthe mask above the second raised structure in accordance with one ormore aspects of the present invention.

FIG. 10 depicts one example of the structure of FIG. 9 after creating ablanket conformal layer of protective material over the non-planarsemiconductor structure in accordance with one or more aspects of thepresent invention.

FIG. 11 depicts one example of the structure of FIG. 10 after creating ablanket conformal layer of filler material above the blanket protectivelayer in accordance with one or more aspects of the present invention.

FIG. 12 depicts one example of the structure of FIG. 11 after polishingthe blanket filler layer and stopping on the blanket protective layer inaccordance with one or more aspects of the present invention.

FIG. 13 depicts one example of the structure of FIG. 12 after furtheretching the blanket filler layer to expose a portion of the blanketprotective layer above portions of the epitaxial structures subsequentlyto be removed in accordance with one or more aspects of the presentinvention.

FIG. 14 depicts one example of the structure of FIG. 13 after patterningthe blanket protective layer to expose the portion of the second raisedstructure sought to be removed in accordance with one or more aspects ofthe present invention.

FIG. 15 depicts one example of the structure of FIG. 14 after removal ofthe exposed portion of the first epitaxial structure above the secondraised structure in accordance with one or more aspects of the presentinvention.

FIG. 16 depicts one example of the structure of FIG. 15 after creating asecond blanket conformal layer of protective material over thenon-planar semiconductor structure in accordance with one or moreaspects of the present invention.

FIG. 17 depicts one example of the structure of FIG. 16 after patterningthe second blanket conformal protective layer to remove the protectivematerial over the first raised structure and the surrounding fillermaterial to expose a portion of the second epitaxial structure sought tobe removed in accordance with one or more aspects of the presentinvention.

FIG. 18 depicts one example of the structure of FIG. 17 after removingthe portion of the second epitaxial structure in accordance with one ormore aspects of the present invention.

FIG. 19 depicts one example of the structure of FIG. 18 after removingthe second blanket conformal protective layer above the second raisedstructure and the surrounding filler material in accordance with one ormore aspects of the present invention.

FIG. 20 depicts one example of the structure of FIG. 19 after removal ofthe filler material above the first blanket conformal protective layerin accordance with one or more aspects of the present invention.

FIG. 21 depicts one example of the structure of FIG. 20 after removal ofthe first blanket conformal protective layer, exposing the two-headedepitaxial structures created by the removal of the portions of theepitaxial structures, in accordance with one or more aspects of thepresent invention.

FIG. 22 depicts one example of the structure of FIG. 21 after recessingthe filler material to expose neck portions of the raised semiconductorstructures in accordance with one or more aspects of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Aspects of the present invention and certain features, advantages, anddetails thereof, are explained more fully below with reference to thenon-limiting examples illustrated in the accompanying drawings.Descriptions of well-known materials, fabrication tools, processingtechniques, etc., are omitted so as not to unnecessarily obscure theinvention in detail. It should be understood, however, that the detaileddescription and the specific examples, while indicating aspects of theinvention, are given by way of illustration only, and are not by way oflimitation. Various substitutions, modifications, additions, and/orarrangements, within the spirit and/or scope of the underlying inventiveconcepts will be apparent to those skilled in the art from thisdisclosure.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about,” is not limited to the precise valuespecified. In some instances, the approximating language may correspondto the precision of an instrument for measuring the value.

The terminology used herein is for the purpose of describing particularexamples only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise” (andany form of comprise, such as “comprises” and “comprising”), “have” (andany form of have, such as “has” and “having”), “include (and any form ofinclude, such as “includes” and “including”), and “contain” (and anyform of contain, such as “contains” and “containing”) are open-endedlinking verbs. As a result, a method or device that “comprises,” “has,”“includes” or “contains” one or more steps or elements possesses thoseone or more steps or elements, but is not limited to possessing onlythose one or more steps or elements. Likewise, a step of a method or anelement of a device that “comprises,” “has,” “includes” or “contains”one or more features possesses those one or more features, but is notlimited to possessing only those one or more features. Furthermore, adevice or structure that is configured in a certain way is configured inat least that way, but may also be configured in ways that are notlisted.

As used herein, the term “connected,” when used to refer to two physicalelements, means a direct connection between the two physical elements.The term “coupled,” however, can mean a direct connection or aconnection through one or more intermediary elements.

As used herein, the terms “may” and “may be” indicate a possibility ofan occurrence within a set of circumstances; a possession of a specifiedproperty, characteristic or function; and/or qualify another verb byexpressing one or more of an ability, capability, or possibilityassociated with the qualified verb. Accordingly, usage of “may” and “maybe” indicates that a modified term is apparently appropriate, capable,or suitable for an indicated capacity, function, or usage, while takinginto account that in some circumstances the modified term may sometimesnot be appropriate, capable or suitable. For example, in somecircumstances, an event or capacity can be expected, while in othercircumstances the event or capacity cannot occur—this distinction iscaptured by the terms “may” and “may be.”

Reference is made below to the drawings, which are not drawn to scalefor ease of understanding, wherein the same reference numbers are usedthroughout different figures to designate the same or similarcomponents.

FIG. 1 depicts one example of a starting structure 100 for a non-planarsemiconductor structure, including a semiconductor substrate 102 of anysuitable semiconductor material (e.g., a silicon wafer) and raisedsemiconductor structures 104 coupled to the substrate. Top surfaces 109and 111 of the structures are exposed, and the structures may include,for example, a raised structure of a first type 106 (e.g., P type) and araised structure of a second type 108 (e.g., N type). As used herein,the term “raised semiconductor structure” refers to a structure that israised with respect to the substrate (e.g., a “fin”), creating anon-planar structure. In one example, the raised structures have beenetched from the same bulk semiconductor as the substrate. A fillermaterial 110 surrounds the raised semiconductor structures, for example,a dielectric (e.g., an oxide).

In one example, substrate 102 may include any silicon-containingsubstrate including, but not limited to, silicon (Si), single crystalsilicon, polycrystalline Si, amorphous Si, silicon-on-nothing (SON),silicon-on-insulator (SOI), silicon-on-replacement insulator (SRI) orsilicon germanium substrates and the like. Substrate 102 may in additionor instead include various isolations, dopings and/or device features.The substrate may include other suitable elementary semiconductors, suchas, for example, germanium (Ge) in crystal, a compound semiconductor,such as silicon carbide (SiC), gallium arsenide (GaAs), galliumphosphide (GaP), indium phosphide (InP), indium arsenide (InAs), and/orindium antimonide (InSb) or combinations thereof; an alloy semiconductorincluding GaAsP, AlInAs, GaInAs, GaInP, or GaInAsP or combinationsthereof.

FIG. 2 depicts one example of the structure 100 of FIG. 1 after masking112 the first raised structure 106 with a protective material. In oneexample, the hard mask is created by blanket deposition and patterningof the protective material, for example, a nitride (e.g., siliconnitride). Where a nitride is used, the deposition may be accomplishedusing, for example, CVD, PECVD or ALD, and the patterning may beaccomplished by, for example, lithography, and may be followed by dry aetch of the nitride.

FIG. 3 depicts one example of the structure 100 of FIG. 2 afterrecessing the second raised structure 108 below a top surface 114 of thefiller material 110 surrounding the raised structures. In one example,where the second raised structure includes n-type silicon, the recessmay be performed by, for example, a wet etch, e.g., ammonia or TMAHsolution, or a combination of dry etch and wet etch.

FIG. 4 depicts one example of the structure 100 of FIG. 3 after creatingan epitaxial structure 116 of a first type on the recessed top surface(118, FIG. 3) of the second raised structure 108. In one example, theepitaxial material for the first epitaxial structure includes a materialthat can act as a channel for the second raised structure. For example,where the second raised structure includes n-type silicon, the epitaxialmaterial may include epitaxial silicon. More broadly, the epitaxialstructure(s) may include one or more materials from Groups III-V of thePeriodic Table of Elements. As one skilled in the art will know,silicon-containing epitaxial material naturally grows intodiamond-shaped structures.

FIG. 5 depicts one example of the structure 100 of FIG. 4 after removalof the mask (112, FIG. 1) above the first raised structure 106. In oneexample, where the mask includes a nitride hard mask, a wet etch, forexample, a hot phosphorus solution, may be used for the mask removal.

FIG. 6 depicts one example of the structure 100 of FIG. 5 after creatinga conformal layer 120 of protective material (i.e., a mask) over thefirst epitaxial structure 116 on the second raised structure 108 andover the top surface (114, FIG. 3) of the surrounding filler material.In one example, where the mask includes a nitride, deposition can beaccomplished using, for example, CVD, PECVD or ALD, for a blanketdeposition, and the patterning may be done with lithography, followed bya dry etch of the nitride or protective material (i.e., remove the maskabove the first raised structure 106).

FIG. 7 depicts one example of the structure 100 of FIG. 6 afterrecessing 122 the first raised structure 106 below a top surface 124 offiller material 110 surrounding the raised structures. In one example,where the first raised structure includes p-type silicon, the recess maybe performed by, for example, a wet etch, e.g., ammonia or TMAHsolution, or a combination of dry etch and wet etch.

FIG. 8 depicts one example of the structure 100 of FIG. 7 after creatinga second epitaxial structure 126 of a second type on the recessed topsurface (122, FIG. 7) of the first raised structure 106. In one example,where the first raised structure includes p-type silicon, the epitaxialmaterial of the second epitaxial structure may be, for example, silicongermanium (SiGe), and may be created by, for example, growing the samevia, e.g., vapor-phase epitaxy, molecular-beam epitaxy or liquid-phaseepitaxy.

FIG. 9 depicts one example of the structure 100 of FIG. 8 after removalof the mask (120, FIG. 8) above the second raised structure 108. In oneexample, where the second raised structure includes n-type silicon, thefirst epitaxial structure 116 includes epitaxial silicon, and the maskincludes a nitride, removal of the mask may be accomplished using, forexample, a wet etch, for example, a hot phosphorus solution.

FIG. 10 depicts one example of the structure 100 of FIG. 9 aftercreating a blanket conformal layer 128 of protective material over thenon-planar semiconductor structure. In one example, the layer ofprotective material includes a nitride, and may be deposited using, forexample, CVD, PECVD or ALD.

FIG. 11 depicts one example of the structure 100 of FIG. 10 aftercreating a blanket conformal layer 130 of filler material above theblanket protective layer. Preferably, the filler material is chosen tobe selectively etchable with respect to the layer of protectivematerial, such that the layer of protective material may act as a stop.In one example, the layer of protective material includes a nitride, andthe conformal layer of filler material includes, for example, an oxide,and may be deposited by, for example, CVD, PECVD or ALD.

FIG. 12 depicts one example of the structure 100 of FIG. 11 afteretching the blanket conformal filler layer 130 and stopping on theblanket protective layer 128. In one example, where the filler materialis an oxide and the layer of protective material includes a nitride, theetch may be performed using, for example, chemical mechanical polishing.

FIG. 13 depicts one example of the structure 100 of FIG. 12 afterfurther etching the blanket filler layer 130 to expose portions (132,134) of the blanket protective layer 128 above portions (136, 138,respectively) of the epitaxial structures (126, 116) subsequently to beremoved. In one example, where the filler material is an oxide and thelayer of protective material includes a nitride, the filler etch may beperformed using, for example, a dry etch, e.g., a plasma etch, a wetetch (e.g., HF or dHF solutions), or a combination of dry etch and wetetch.

FIG. 14 depicts one example of the structure 100 of FIG. 13 afterpatterning the blanket protective layer 128 to expose the portion 138 ofthe first epitaxial structure 116 sought to be removed. In one example,where the filler material includes an oxide, the layer of protectivematerial includes a nitride, and the epitaxial material of the firstepitaxial structure includes epitaxial silicon, the protective layerpatterning may be performed using, for example, lithography, and may befollowed by a dry etch of the nitride portion 138.

FIG. 15 depicts one example of the structure 100 of FIG. 14 afterremoval of the exposed portion (138, FIG. 14) of the first epitaxialstructure 116 above the second raised structure 108. In one example,where the filler material is an oxide, the layer of protective materialincludes a nitride and the epitaxial material of the first epitaxialstructure includes epitaxial silicon, the first epitaxial structure etchmay be performed using, for example, a wet etch, e.g., ammonia or TMAHsolution, or a hybrid method with a combination of dry etch and wetetch. Note that the epitaxial silicon is crystal and the etch followsthe crystal orientation.

FIG. 16 depicts one example of the structure 100 of FIG. 15 aftercreating a second blanket conformal layer 140 of protective materialover the non-planar semiconductor structure. In one example, where thefiller material 130 is an oxide, the first layer of protective material128 includes a nitride and the epitaxial material of the first epitaxialstructure 116 includes epitaxial silicon, the second conformal layer ofprotective material may be, for example, a nitride and depositionthereof may be performed using, for example, CVD, PECVD or ALD.

FIG. 17 depicts one example of the structure 100 of FIG. 16 afterpatterning the second blanket conformal protective layer 140 to removethe protective material over the portion 136 of the second epitaxialstructure 126 sought to be removed and the surrounding filler material130. In one example, where the second protective layer 140 includes anitride, deposition thereof can be accomplished using, for example, CVD,PECVD or ALD, and the patterning thereof may be done with lithography,followed by a dry etch of the nitride or protective material.

FIG. 18 depicts one example of the structure 100 of FIG. 17 afterremoving the portion (136, FIG. 17) of the second epitaxial structure126. In one example, where the layer 130 of filler material is an oxide,both layers (140, 128) of protective material include a nitride and theepitaxial material of the second epitaxial structure 126 includesepitaxial silicon germanium, the second epitaxial structure etch may beperformed using, for example, a wet etch, e.g., ammonia or TMAHsolution, or a hybrid method with combination of dry etch and wet etch.Note that the epitaxial silicon germanium is crystal and the etchfollows the crystal orientation.

FIG. 19 depicts one example of the structure 100 of FIG. 18 afterremoving the second blanket conformal protective layer (140, FIG. 18)above the first epitaxial structure 116 and the surrounding fillermaterial 130. In one example, where the filler material is an oxide,both layers of protective material include a nitride, the epitaxialmaterial of the first epitaxial structure includes epitaxial silicon andthe epitaxial material of the second epitaxial structure includesepitaxial silicon germanium, removal of the remaining second protectivelayer may be accomplished using, for example, a wet etch, e.g., a hotphosphorus solution.

FIG. 20 depicts one example of the structure 100 of FIG. 19 afterremoval of the filler material (130, FIG. 19) above the first blanketconformal protective layer 128. In one example, where the fillermaterial is an oxide, the first layer of protective material includes anitride, the epitaxial material of the first epitaxial structure 116includes epitaxial silicon and the epitaxial material of the secondepitaxial structure 126 includes epitaxial silicon germanium, removal ofthe filler material may be accomplished using, for example, a wet etch,or a combination of dry etch and wet etch.

FIG. 21 depicts one example of the structure 100 of FIG. 20 afterremoval of the first blanket conformal protective layer (128, FIG. 20),revealing the multi-headed (two heads in this example) epitaxialstructures (126, 116) created by the removal of the portions of theepitaxial structures (e.g., heads 142 and 144 of epitaxial structure116). In one example, where the filler material is an oxide, the firstlayer of protective material includes a nitride, the epitaxial materialof the first epitaxial structure includes epitaxial silicon and theepitaxial material of the second epitaxial structure 126 includesepitaxial silicon germanium, removal of the remaining first protectivelayer may be accomplished using, for example, a wet etch, e.g., a hotphosphorus solution.

FIG. 22 depicts one example of the structure 100 of FIG. 21 afterrecessing the layer 110 of filler material to expose neck portions (146,148) of the raised semiconductor structures (106, 108, respectively). Inone example, where the filler material surrounding the raised structuresis an oxide, the material of the first raised structure is p-typesilicon, the material of the second raised structure is n-type silicon,the epitaxial material of the first epitaxial structure 116 includesepitaxial silicon and the epitaxial material of the second epitaxialstructure 126 includes epitaxial silicon germanium, etching of thefiller material to expose the necks may be accomplished using, forexample, a dry etch, wet etch, COR (chemical oxide removal) etch or acombination thereof. Further, in the present example, the epitaxialstructures together with their respective necks each resemble a Y-shape(150, 152).

While several aspects of the present invention have been described anddepicted herein, alternative aspects may be effected by those skilled inthe art to accomplish the same objectives. Accordingly, it is intendedby the appended claims to cover all such alternative aspects as fallwithin the true spirit and scope of the invention.

The invention claimed is:
 1. A method, comprising: providing asemiconductor structure, the structure comprising a semiconductorsubstrate, at least one first raised semiconductor structure of a firsttype coupled to the substrate, and at least one second raisedsemiconductor structure of a second type coupled to the substrate;growing at least one first epitaxial structure on a first top surface ofone or more of the at least one first raised structure, wherein the atleast one first epitaxial structure comprises at least one firstepitaxial material; growing at least one second epitaxial structure on asecond top surface of one or more of the at least one second raisedstructure, wherein the at least one second epitaxial structure comprisesat least one second epitaxial material; increasing a first surface areaof the at least one first epitaxial structure by removing a top portionthereof, the top portion having bottom sides longer than top sidesthereof; increasing a second surface area of the at least one secondepitaxial structure by removing a top portion thereof, the top portionhaving bottom sides longer than top sides thereof; wherein thesemiconductor structure further comprises a filler layer of at least onefiller material conformally surrounding the at least one first raisedstructure and the at least one second raised structure while exposingthe first top surface and the second top surface, and wherein: growingthe at least one first epitaxial structure comprises: masking the atleast one second raised structure; recessing the exposed first topsurface below a top surface of the filler layer; and growing the atleast one first epitaxial structure on the recessed first top surface;and growing the at least one second epitaxial structure comprises:masking the at least one first epitaxial structure; recessing theexposed second top surface below a top surface of the filler layer; andgrowing the at least one second epitaxial structure on the recessedsecond top surface.
 2. The method of claim 1, wherein the removingcreates a depression with an epitaxial head structure on opposite sidesof the depression.
 3. The method of claim 1, wherein the increasingcomprises: creating a conformal first layer of a first material over thefiller layer, the at least one first epitaxial structure and the atleast one second epitaxial structure; conformally covering the firstlayer with a second layer of a second material having etchcharacteristics selective to the first layer; and etching the secondlayer to expose the first layer over one or more portions of each of theat least one first epitaxial structure and the at least one secondepitaxial structure.
 4. The method of claim 3, wherein etching thesecond layer comprises: etching the second layer using the first layeras an etch stop; and further etching the second layer to perform theexposing.
 5. The method of claim 4, further comprising: removing thefirst layer over the one or more portions of the at least one firstepitaxial structure; and etching the one or more portions from the atleast one first epitaxial structure.
 6. The method of claim 5, furthercomprising, after etching the one or more portions from the at least onefirst epitaxial structure: conformally covering exposed portions of theat least one first epitaxial structure with a layer of the firstmaterial; removing the first layer over the one or more portions of theat least one second epitaxial structure; and etching the one or moreportions from the at least one second epitaxial structure.
 7. The methodof claim 6, further comprising, after etching the one or more portionsfrom the at least one second epitaxial structure, removing remainingfirst material covering the semiconductor structure.
 8. The method ofclaim 7, further comprising, after removing the remaining first materialcovering the semiconductor structure: removing the second layer of thesecond material to expose the first layer of the first material; andremoving the first layer of the first material to expose the at leastone first and the at least one second epitaxial structure.